The present invention relates to an apparatus and method for inspecting defects, adapted to detect and analyze contamination and other defects occurring during the manufacturing processes of a desired object that include forming patterns on a substrate, to provide appropriate measures against contamination and other defects, and to inspect the occurrence status thereof. The manufacturing processes include semiconductor manufacturing processes, liquid-crystal display device manufacturing processes, printed-circuit board manufacturing processes, and the like.
During conventional semiconductor-manufacturing processes, the presence of dust particles or other foreign substances (hereinafter, referred to collectively as contamination) on the surface of a semiconductor substrate (wafer) causes defects such as the improper insulation or short-circuiting of wiring. In addition, if a semiconductor device becomes fine-structured to form fine-structured contamination in the semiconductor substrate, the formation of the contamination results in the improper insulation of capacitors and/or in damage to gate oxide films or the like. Such contamination gets entrapped in various forms for various reasons. For example, the contamination may have stemmed from the movable section of a transport device, from the human body, or from an internal reaction product of a processing device due to a process gas, or may have been included in a chemical or a material. The occurrence of contamination or some other defect on patterns during liquid-crystal display device manufacturing processes similar to the above manufacturing processes renders the display device inoperative. The same situation also arises during printed-circuit board manufacturing processes; the presence of contamination causes pattern short-circuiting and/or improper connection.
A known technique for inspecting the above-mentioned contamination is by irradiating a wafer with coherent light, spatially filtering away the light exited from an iterative pattern present on the wafer, and detecting non-repeatable contamination or other defects in edge-enhanced form. Also, Japanese Laid-Open Patent Application Publication (JP Kokai) No. Hei 01-117024 (Patent Document 1) discloses a contamination inspection apparatus constructed such that a circuit pattern formed on a wafer is irradiated from a direction inclined at 45 degrees to a major straight-line group of the circuit pattern to prevent the zeroth-order diffracted light from the major straight-line group from being input to an aperture of an objective lens. It is also described that in the conventional technique of Patent Document 1, straight lines not belonging to the main straight-line group are light-shielded with a spatial filter. In addition, other known apparatuses and methods for inspecting contamination and other defects are described in JP Kokai Nos. Hei 06-258239 (Patent Document 2), Hei 08-210989 (Patent Document 3), 2000-105203 (Patent Document 4), 2004-93252 (Patent Document 5), 2004-177284 (Patent Document 6), and 2004-184142 (Patent Document 7). That is to say, Patent Documents 2 and 7 describe a technique using a pitch-variable spatial filter. Patent Document 3 describes a technique in which, after a plurality of light fluxes spatially incoherent with each other have been obtained by splitting a beam emitted from a laser source and combining mirrors for the fluxes to differ from one another in optical path length, a desired section on a substrate is irradiated with the obtained plurality of fluxes obliquely at mutually different angles of incidence and then the reflected/scattered light arising from very small defects on the substrate during the irradiation is converged via detection optics and received with photoelectric conversion means. Patent Document 7 further describes a technique using various forms of spatial filters, inclusive of a transmissive type of liquid-crystal filter. Patent Documents 4, 5, and 6 describe an apparatus for inspecting defects such as contamination, equipped with highly efficient illumination optics to emit a slit-shaped beam of illumination light from a direction of 45 degrees for reduced incidence of pattern-scattered light on an objective lens.